Titanium alloy becomes important aeronautical material for its high strength, strong corrosion resistance, etc. The use of the titanium alloy is significant for reducing the weight of a plane and improving the performance of the plane. Although having favorable corrosion resistance, titanium alloy is liable to contact corrosion resulting in failure under synergetic effect of stress and environment when titanium alloy contacts with aluminum alloy and alloy steel.
Contact corrosion is galvanic corrosion, namely that when dissimilar metals are in contact in the same media, due to different electrode potentials the metal with lower electrode potential melts preferentially to another resulting in local corrosion of the contacting part of the metal. The essential measure for controlling contact corrosion is to appropriately carry out surface modification and surface coating treatment through reasonable material selection to make the electrode potentials of dissimilar materials of contacting members nearly equal so as to reduce or eliminate contact corrosion. In aviation industry, main measures for preventing contact corrosion between titanium alloy and its connecting structure includes various surface engineering technologies. In one measure, the surfaces of materials are modified by chemical plating, electroplating, and the like, whereby the electrode potentials of the contacting materials are nearly equal to effectively prevent galvanic corrosion. For instance, all titanium alloy fasteners of a B767 airliner are treated with ion plating aluminum before contacting with aluminum alloy, so that the galvanic effect of titanium-aluminum is reduced; anodic oxidation or chemical conversion coating treatment is another way for reducing contact corrosion of titanium alloy contacting with aluminum contacting and alloy steel. Painting or glue coating is also an important method for preventing contact corrosion between titanium alloy and other metals, such as epoxy zinc yellow primer, XM-33-4 two-component sealant protection, which can prevent galvanic corrosion when 0Cr13Ni8Mo2Al contacts with LY12 and TC4.
Though there have been certain achievements in preventing contact corrosion of titanium alloy at home and abroad, the above current measures have some problems. The common problem lies in that the coating obtained by the above method is easy to flake off under the action of contact corrosion, and abrasive wear is generated among contacting parts due to flaked pieces, so that the failure of the parts is aggravated to cause completely loss of the protective effect of the coating. In addition, the technical measures of the prior art have high cost and is limited to the size and the shape of a work piece to be processed, thereby having great limitation, and a large number of fasteners of a plane are in urgent need to solve the problem of failure caused by contact corrosion.